The three organic two‐photon‐absorbing cycloalkanone chromophores 2,4‐bis[4‐(diethylamino)benzylidene]cyclobutanone, C₂₆H₃₂N₂O (I), 2,5‐bis[4‐(diethylamino)benzylidene]cyclopentanone, C₂₇H₃₄N₂O (II), and 2,6‐bis[4‐(diethylamino)benzylidene]cyclohexanone, C₂₈H₃₆N₂O (III), were obtained by a reaction between 4‐(diethylamino)benzaldehyde and the corresponding cycloalkanone and were characterized by single‐crystal X‐ray diffraction studies, as well as density functional theory (DFT) quantum‐chemical calculations. Molecules of this series have three main fragments, i.e. central acceptor (A) and two terminal donors (D₁ and D₂) and represent examples of the D₁–π–A–π–D₂ molecular design. All three compounds crystallize with two crystallographically independent molecules in the asymmetric unit (A and B) and are distinguished by the conformations of both the molecular Et₂N—C₆H₄—C=C—C(=O)—C=C—C₆H₄—NEt₂ backbone (arcuate or linear) and the terminal diethylamino substituents (syn‐ or antiperiplanar to the plane of the molecule). The central four‐ and five‐membered rings in I and II are almost planar, and the six‐membered ring in III adopts a sofa conformation. In the crystals of I–III, the two independent molecules A and B form hydrogen‐bonded [A…B] dimers via intermolecular C—H…O hydrogen bonds. Furthermore, the [A…B] dimers in I are bound by intermolecular C—H…O hydrogen bonds into two‐tier puckered layers, whereas in the crystals of II and III, the [A…B] dimers are stacked along the c and a axes, respectively. Taking into account the decreasing steric strain upon expanding the central ring, compound I might be more efficient as a two‐photon absorption chromophore than compounds II and III, which corresponds to the results of spectroscopic studies.

中文翻译：

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有机双光子吸收环烷酮发色团的合成与结构研究。

三种有机的吸收两个光子的环烷酮发色团2,4-双[4-（二乙基氨基）亚苄基]环丁酮，C ₂₆ H ₃₂ N ₂ O（I），2,5-双[4-（二乙基氨基）亚苄基]环戊酮，C ₂₇ H ₃₄ N ₂ O（II）和2,6-二[4-（二乙氨基）亚苄基]环己酮，C ₂₈ H ₃₆ N ₂ O（III）是通过4-（二乙氨基）苯甲醛与相应的环烷酮之间的反应获得的，并通过单晶X射线衍射研究以及密度泛函理论（DFT）量子化学计算进行了表征。该系列的分子具有三个主要片段，即中央受体（A）和两个末端供体（D ₁和D ₂），代表D ₁ –π– A –π– D ₂分子设计的实例。所有这三种化合物均以不对称单元中的两个晶体学独立分子结晶（A和B）并通过分子Et ₂ N-C ₆ H ₄ -C = CC （= O）-C = CC ₆ H ₄ -NEt ₂主链（弓形或线性）的构象来区分二乙氨基取代基（与分子平面同平面或反平面）。I和II中的中央四元和五元环几乎是平面的，III中的六元环采用了沙发构型。在I – III晶体中，两个独立的分子A和B形成氢键[ A … B]二聚体经由分子间C-H ... O氢键。此外，I中的[ A … B ]二聚体通过分子间C–H…O氢键结合成两层褶皱层，而在II和III晶体中，[ A … B ]二聚体沿c堆积和一个轴。考虑到中心环膨胀时空间应变的降低，化合物I作为双光子吸收发色团可能比化合物II和III更有效。，这与光谱研究的结果相对应。